This invention relates, in general, to molds, and more particularly, to an aid for moving a mold on the platen of a mold press.
Many semiconductor devices are encapsulated in a plastic material. The encapsulation process involves the use of a mold and a mold press. Typically the mold comprises two mold halves wherein the mold halves form a plurality of cavities therebetween. The semiconductor devices are placed in the cavities and the plastic encapsulating material is injected into the cavities and cured to encapsulate the semiconductor device. To keep the encapsulating material from escaping from between the two mold halves, the molds are placed in a hydraulically operated press and held together under extremely high pressures. Accordingly, the mold halves are made of metal and typically weigh more than one or two individuals can safely handle.
In the past, the mold was transported to the press on a cart. Some carts were equipped with a roller or roller ball array to facilitate movement of the mold on the cart. The cart was provided with a fence or rail assembly in order to prevent the mold from accidentally rolling off the cart. The cart had a mechanical aid to assist in raising and lowering the height of the cart so that the mold could be easily transferred to a lower platen of a mold press. However, once the mold was on the platen high friction had to be overcome in order to position the mold in the central region of the mold press. Once the mold was near the center of the platen, the mold was floated on an air bearing generated by emitting compressed air to ports near the platen center. This allowed precise manual location of the mold in relation to the mold press features such as the transfer ram. During the positioning of the mold to near the center of the platen various devices such as levers (wooden or metal) were manually used to jockey the mold toward the center of the platen. This consumed considerable amount of manpower and time and usually resulted in scratching or scoring the platen itself.
Accordingly, it is an object of the present invention to provide means for easily moving a mold to a central region of a mold press.
Another object of the present invention is to provide a mold handling aid for moving a heavy mold on a platen of a mold press.
Yet another object of the present invention is to provide means to allow one individual to easily move a large mold on a platen of a mold press.
Yet a further object of the present invention is to provide roller means on a mold which do not interfere with compression of the mold in a mold press.